Blood pumps

Abstract

A blood flow assist system can include an impeller assembly including an impeller shaft and an impeller on the impeller shaft, a primary flow pathway disposed along an exterior surface of the impeller. The system can include a rotor assembly at a proximal portion of the impeller shaft. A secondary flow pathway can be disposed along a lumen of the impeller shaft. During operation of the blood flow assist system, blood can be pumped proximally along the primary flow pathway and the secondary flow pathway. The system can include a sleeve bearing distal the impeller. The system can include a drive unit having a distal end disposed distal a proximal end of the second impeller. The drive unit comprising a drive magnet and a drive bearing between the drive magnet and the impeller assembly.

What is claimed is: 
     
         1 . A blood flow assist system comprising:
 an impeller assembly comprising a rotor assembly and an impeller coupled with the rotor assembly, the rotor assembly comprising a concave bearing surface; and   a drive unit proximal the impeller assembly, the drive unit comprising a drive magnet and a drive bearing between the drive magnet and the impeller assembly, the drive bearing comprising a convex bearing surface shaped to fit within the concave bearing surface, the convex bearing surface comprising a plurality of distally-projecting segments, the plurality of distally-projecting segments spaced apart circumferentially to define at least one channel between adjacent segments.